dockPeek

The most common complaint from Windows-to-Mac switchers: the Dock can't preview windows like the Windows taskbar. dockPeek fixes that — hover a Dock icon for half a second, and a panel of live thumbnails of every window for that app appears. Click goes straight to the window.

Problem

• macOS Dock only switches apps, not individual windows
• Mission Control is heavy and not "instant"
• Most third-party tools rely on private APIs and break on every macOS update

Solution

Pure public APIs + high-performance capture:

1. AXUIElement Dock observation: Accessibility API detects which Dock icon the cursor is on — no polling, no CPU waste.
2. ScreenCaptureKit thumbnails: macOS 12.3+ official API, 5x faster than the legacy CGWindowListCreateImage and Retina-aware.
3. SwiftUI preview panel: NSPanel (not NSWindow) avoids stealing focus; CALayer transforms power smooth entry animation.
4. Spaces / Mission Control aware: Lists windows from other Spaces too, and clicking switches Spaces.

Stack

• UI: SwiftUI 5 + AppKit (NSPanel)
• Accessibility: AXUIElement API
• Screen capture: ScreenCaptureKit (macOS 12.3+)
• Window management: CGWindowListCopyWindowInfo + Spaces API

Outcomes

• Working release shipped
• Integrates seamlessly with native Dock behavior
• 60fps preview, < 2% CPU at idle
• Public APIs only — high forward compatibility with macOS updates

Lessons

• AXUIElement is the hidden gem of Mac automation: Many people assume Dock interaction needs private APIs — the public AX API is enough.
• ScreenCaptureKit is a game-changer: Way faster than the old API, native multi-display + Retina support. Most "laggy Mac utility" complaints went away after this API shipped.
• NSPanel vs NSWindow: For floating UI, NSPanel is the right choice. NSWindow steals focus and breaks the Dock interaction.